Assig-nob



inggelatine reliefplates UNITED STATES PATENT OFFICE;

.PHILIP H. MANDEL, OF BOSTON, MASSACHUSETTS, ASSIGNOB, BY MESNE ASSIGNMENT, TO THE MECHANICAL COMPANY, OF NEW YORK, N. Y.

ART OF MAKING GELATINE RELIEF-PLATES.

SPECIFICATION forming part of Letters Patent No. 24=O,524,-dated April 26, 1881.

Application filed December 24, 1880. (N0 specimens.)

To all whom t't may concern:

Be it known that I, PHILIP H. MANDEL, of Boston, in the county of Suffolk and State of Massachusetts, have invented certainlmprovements in the Art of Making Gelatine Relief- Plates, of which the following is a specification.

This invention relates to the processof makfrom which to form electrotypes for printing, and it-has for its object to produce a relief-plate from which an electrotype in intaglio can be produced, and also to insure perfect contact between the sensitized gelatine and the photographic negative used in producing gelatine relief-plates.

To these ends my invention consists, as a whole, in applying to the collodion side of a photographic negative a protecting-coat,

formed as hereinafter described, to strengthen the collodion negative and protect the same against the action of warm water, then placing the sensitized gelatine directly upon said coat, exposing the negative to light to harden the portions of the gelatine not protected by the negative, and then washing the gelatine with warm water to remove the sensitive portions, thus exposing the protecting-coat and leaving the hardened portions of the gelatine in relief thereon. By this. process I obviate any liability of separation between the negative and the gelatine, and produce a reliefplate which is adapted for the production of an electrotype in intaglio, the hardened portions of the gelatine being hardest at the inner portion of the gelatine coating which is in contact with the protecting-coat of the negative, so that the hardened gelatine can withstand the amount of washing necessary to entirely remove the sensitive gelatine and expose the portions of the strengthening-coat which it covers. Said film is absolutely parallel with the surface of the negative glass to which it is applied; hence it forms a surface as smooth and level as the glass, and adapted to form a like surface on an intaglio electrotype-plate.

In carrying out. my invention, I take a photographic negative and apply to its printed or collodion side a thin transparent protectingfilm adapted to resist the action of warm water and adhere closely to the lines of the negative tograph, very and the portions of the surface of the negative glass not covered by the lines of the negative. This coat I make as follows: Take a solution composed of india-rubber dissolved in benzine and of about the consistency of sweet-oil.

.Pour this solution upon the printed side of the glass and allow it to run 0E until only an extremely thin film remains.

Expose this film to the air until enough of the benzine evaporates to partially harden the film, leavin g it slightly sticky; then apply to this sticky surface a mixture composed of about twenty grams of raw collodion and five drops of castor-oil, or any other suitable oil, thus forming another thin film, which adheres closely to the first and is allowed to become entirely dry. The protecting-film is now completed and ready for the sensitized gelatine, which I prefer to make as follows: Dissolve in four hundred parts of water one hundred parts of gelatine and twenty-five parts of sugar; add to this ten parts of glycerine, biehromate of ammonia, and five parts of ammonia. This sensitized gelatine is applied to the protecting-coat of the negative, and when ready for the relief process the negative is exposed to light in the usual manner, to harden the portions of the gelatine not protected by the negative. The gelatine is then washed to entirely remove the sensitive portions, leaving the hardened portions in relief upon the protecting-coat of the negative.

The relief plate thus produced may be electrotyped upon in the usual manner to produce an electrotype-plate in intaglio; or, if an electrotype in relief is desired, a mold can be taken from the relief-plate and an electrotype taken from the mold.

I have found by extended practical tests that by applying the gelatine directly to the negative, instead of to a separate plate, I am able to produce a perfect fac-simile of the phofine lines being faithfully reproduced.

I am aware that it is not new to apply bichromated gelatine in the manufacture of gelatine relief-plates; hence I do not claim such application, broadly.

I claim 1. The improvement in the art of making eight parts of to a photographic negative gelatine relief-plates, the same consisting in applying. to the collodionside of a photographic negative a tough, adhesive, and transparent protecting-coat composed of a film of indiarubber in contact with the negative, and a film of raw collodion and oil placed upon the firstnamed film, placing the sensitized gelatine directly upon said coat and treating the gelatine by exposure to light to harden the portions not protected by the negative, and by Washing to remove the soft portions of the gelatine, and thereby leave the hardened portions in relief upon the protecting-coat, as setforth.

2, The method herein described of protecting or strengthening the collodion side of a photographic negative to prepare it for a coatlng of sensitized gelatine,.and protect it from the last film to become 

